Mail sorting apparatus is in wide use today for detecting a postal code number for a zone improvement program code described on each mail item, such as a postcard or a sealed letter. The detection of information utilized in the sorting process is possible when other postal information such as return addresses and advertising blocks are ignored. When the addressee's name and address are uniquely located on a mail item, reading of this information is enhanced for the sorting procedure. The location of an address block on an envelope containing the destination address has been performed using such systems as described in U.S. Pat. No. 4,013,999.
The addressee's address may be localized in a "window" area position on the letter mail item. The window area may be formed to allow the addressee's address contained on an enclosed letter to be visible through the envelope. The window area may be provided with a substantially transparent medium, such as, for example, a glassine window or cellophane film. Additionally, the window area may be a cutout in the envelope itself with no transparent covering. As used herein, the window area may also include a lable pasted on the outside of the envelope, where the label contains the destination address.
The present invention is utilized for assisting mail sorting apparatus in the location of an address block by detecting the location of a window contained on the letter mail item. The letter mail sorting apparatus independently detects the presence of lines of print on the letter mail item and utilizes information provided by the present invention relating to the presence of a window for assisting and determining the location of address blocks contained on the letter mail item. With the detection of a window area, it is more likely that the lines of print on the letter mail item detected by the mail sorting apparatus does, in fact, contain the destination address block containing the address for sorting purposes. A need has thus arisen for a window detection system capable of locating various types of windows contained on a letter mail item including, for example, labels, glassine windows and cutout windows.